Finally got my sts tt kit installed and it went pretty good. Took it to a tuner , xtreme motorsports, and they had it over night and all day today. I was really excited to get it and drive it today expecting 550+ rwhp based on what I've seen from others. I got 50lb injectors, new spark plugs ect with the kit. I picked up the car today and they said they could only get 425 rwhp with a "max" of 6 psi because the valve springs need upgraded. Sts says at 7 psi I should make 530 rwhp on stock block. I'm not mechanically inclined but something seems wrong here, ideas?

 

First thing Id check for would be a boost leak. Search on here there is a TON of info on this! But yes those numbers seem very low for that kit.

 

Something isn't right, I have got 500+ out of stock bottom end LS6 in the older C5 Z06's.

 

I agree, the kit should go over 500 easy. Sounds like a possible boost leak.

 

I have to be honest. I would remove my car from that shop and find a reputable and knowledgeable FI tuner to clean up the mess.

Anyone who tells you the VALVE SPRINGS are only good for 425 RWHP is either A) clueless or B) unscrupulous.

 

Ok I'll explain what I see since I don't have a PDF copy yet to paste here.

Boost steadily increases and maxes to 6 psi at about 3900 rpm, stays flat till 4400 rpm, then falls to 4 psi till 5600 rpm, spikes back to 6 psi and falls back right away. I know thats not as good as a picture but that's the best I can do for now.

It's consistent like that across 3 runs.

Is that what a boost leak might look like on paper?

 

To be clear, they said I was probably "floating the valves" and that's why I could not hold boost. I was thinking like you, take it to another shop, but wanted to get opinions here first. Thanks all for your input so far!!


Also, the car has 80k miles on it but has been very well maintained, not sure if that could indicate any issues.

 

Check for exhaust and intake leaks.

 

Will that cause that big of a dyno difference?

With all the couplers and piping with this kit it wouldn't surprise me if there was a leak

 

Valve float is mostly a result of excessive RPM and/or a cam that's too aggressive for the strength of the springs. Basically what they're saying is that your valve springs are being so overtaxed that they don't have the strength to keep the lifters pressed against the camshaft. Thus, the theory is, the valves hang open too long and the pressurized air the turbos are shoving in is escaping right back out the exhaust valves before it can be used.

The theory would make sense if it weren't for the fact that you have a (presumably) stock LS2 engine that's meant to rev to 6000 RPM and they're telling you you're floating valves BELOW that level.

 

I second that you should have a different shop look at it! A trick I liked to use with turbo setups is to use hairspray to lube the couplers when installing them. Helps putting them on and creates a seal once it drys. deff sounds like a leak though.

 

Well yes and no....

In boosted applications it's important to remember boost pressure is acting against the intake valve which in turn reduces valve seat pressure. In this case though 6 psi is hardly enough to worry with....

 

One of the first things you change when going FI, even on a stock motor, is the valvesprings. I agree that leaving the stock springs in should have never been an option.

I also agree, as a former owner of a STS car, that boost leaks are common and aggravating with the system. The only way to truly test it is close off and pressurize the cold side. There are many how-tos on this. Just tightening down the clamps isnt enough. Also, use t-bolt clamps vs the garbage that comes with the kit.

 

Honestly, unless doing a cam at the same time, I don't know a single person who has changed valvesprings going to FI.

I'm sure it's not a bad idea, but it's not something I've ever seen done.

 

Anyone know of a trustworthy tuner in the phx area?

 

Let me clarify a few things here, Xtreme Motorsports did not install this kit. We were contracted to tune this car for the customer. We gave the car a visual inspection before running on the dyno and everything seems to be in order. Performed the drivablity tuning the afternoon the car was dropped off, finished up around noon and strapped it to the dyno. We proceeded to work on the full throttle tuning that afternoon. Inital dyno runs were not performed by our shop prior to the kits installation so no baseline numbers. On the first pull the valve cover gaskets spewed oil over the engine, after contacting the customer we replaced the gaskets. Continuing on with the tuning after the leak was repaired, we noticed that the initial runs were quite low, zeroing in on the AFR we picked up some HP, and noticed that the boost was lower that what the kit should produce, pushed the timing up to point of 1 deg of knock and backed back down to zero knock, as we have done hundreds of times before. We even let the car sit and cool off before a final dyno run was performed, still low boost falling off upper rpm ranges, with subpar HP numbers.
We recommended a valve spring change due to the power falling flat in the upper rpm ranges, we also recommended increasing the wastegate springs or installing a boost controller, this is all assuming that the kit was installed correctly. I have tested many valve springs over the years and find that with 80,000 miles springs seem to loose strength and seat pressure, even seen some broken ones over the years. We offered our help to repair the car and help the customer achieve his goals, at his expense of course. (we did not sell the kit or install it) At this time I am not sure what he expects us to do.

I really don't feel that taking the car to another shop for simply a tune will resolve anything other than more expense that could be used to fix the current problems with the kit. AFR and Timing is correct and the car runs perfectly during normal and boosted driving. No magic tune will pick up 100 more HP.

I will post up a dyno run for those that want to take a look. You can see that the boost never hit 6 psi averaged around 4.5 could be a boost leak but we feel that there is more to it than that.

 

Take a look at video from some of the forced induction vehicles we have tuned at our shop, FI accounts for more than 80% of our business with many satisfied customers.

http://xtrememotorsportsracing.com/x...otorsports-tv/

 

When I read the initial post, I kind of glossed over the fact that he had even mentioned the shop by name. I checked out your website after the fact and it certainly portrayed your shop as a pretty professional operation to me.

I was under the impression that your shop had installed the kit (presumably incorrectly). I should have clarified that I wasn't implying there was 100 hp missing out of the tune alone.

The boost level still seems VERY low to be pushing through valve springs to me but after hearing your side, it certainly seems like there are a NUMBER of things going on there.

 

There is always more to the story.

Just trying to help the customer get to his goal without spending a ton of money bouncing from shop to shop.

 

From the sound of pushing oil out of the valve covers, it seems the crank case is pressurizing. Thats problem 1 of ?? that can be found. boost leaks are something to look for. THe STS C5Z06 I had, had leaks at the slip joints.

I would lean heavy on one of those 2 causing issues. Yeah the valve springs could* be causing some issues, but there are plenty of others out there that are running boost on stock block cars with more miles. Granted anything is possible at this point in time.